More than 10 million patients suffer from diabetes in Japan in 2011 and this number is the sixth largest in the world. Diabetes is a serious condition causing complications such as retinopathy and gangrene in its severe stage and having a risk of losing their life due to such a complication. It has been said that, Japanese have constitutional factors to be insensitive to consumption of what one has eaten and to be easy to accumulate them, and thus Japanese are liable to diabetes. Therefore, taking an ingenuity of how to ingest diets and/or enforcement of exercise are recommended for preventing diabetes and progress into severe disease.
A pre-diabetic condition includes a hyperglycemic condition. It is necessary at a stage of the hyperglycemic condition to regularly figure out a blood glucose level, keep a lifestyle not to increase the blood glucose level and improve a lifestyle increasing the blood glucose level. If it is possible to regularly figure out a blood glucose level by non-invasive and always-collectable specimen, self-medication at home can be achieved.
Cystatin is a set of peptide group having an antioxidant effect. Patent Literature 1 describes that cystatin-C can be used as a biomarker when diabetes is detected. Patent Literature 2 describes that cystatin-C can be used as an examination parameter for the diabetes. Patent Literature 3 describes that a diagnosis agent containing an anti-cystatin-SN antibody for colorectal cancer and/or colorectal polyp has been described in. Cystatin-C is present abundantly in semen and spinal fluid and present in only a small amount in saliva. Meanwhile, cystatin-SN is present mainly in saliva and tears.
Basic salivary proline-rich protein 1 and basic salivary proline-rich protein 2 are one type of proline-rich proteins (proline-rich peptides) comprising a proline-rich non-periodically amino acid sequence moiety. Non-Patent Literature 1 describes that the expression of the proline-rich peptide in salivary grands in diabetes model rats was decreased compared with that in the control group and the decreased expression of the proline-rich peptide in the diabetes model rats was improved by administration of insulin.